When fine ore is used in an iron blast furnace, this ore has to be converted into coarser form in order that it might be possible to charge the furnace with the ore. To this end, the ore is sintered in a separate sintering plant, often located immediately adjacent to the blast furnace. There are two fundamental types of sintering plants; belt sintering plants and pan sintering plants. In belt sintering plants, the sinter goods are supplied onto a moving grate, which transports the sinter goods through the different treatment steps. It is common practice to construct the grate of the belt sintering plant to have the shape of a conventional conveyor, but belts composed of consecutive grate carriages are also used.
In the Swedish Pat. No. 330,392, a belt sintering plant is disclosed wherein the belt has been made circular, whereby the construction may be somewhat simplified and the operating conditions improved from the user's point of view. In the same patent, a thorough clarification is also found of the different steps in the sintering process and of the design and advantages of the conventional belt sintering plant and of the circular belt sintering plant.
The pan sintering plant differs from the belt sintering plant in that the grates therein have been made stationary and the other treatment equipment has been made movable. The pan sintering plant may be provided with a straight or circular layout. Since the different components of a pan sintering plant are movable, they cannot be structurally designed to be as complex as those in a belt sintering plant, and the equipment of the different steps cannot be mutually connected. On the other hand, the design and structure of the pan sintering plant can be made considerably more simple and less space-consuming because it is possible to omit the belt, which is difficult to maintain in an operative condition, and to replace it by a few moving units performing the different treatment steps.
An essential component in the pan sintering plant is the ignition carriage, which moves above the grate to be positioned over each pan in its turn and ignites the sinter mixture. At present the ignition of the sinter goods takes place in two steps in the most modern designs: first, using the full power of the burners (usually oil burners) to ignite the sinter goods and, subsequently, using their partial power to maintain and equalize the burning. Since it is exceedingly awkward to connect any kind of gas pipes to the moving sintering carriage, the ignition is exclusively accomplished with the aid of oil, and the requisite combustion air is drawn from the air in the sintering plant with the aid of a blower and conducted to the burners by a separate pipe system. In all designs known in the prior art, because the cover must be simply constructed, a massive frame is used in the cover, consisting either totally of cast plates or of cast plates fitted and braced in a steel structure. The inner surface of the cover is provided with refractory masonry in order to prevent excessive heating of the frame. The greatest difficulty in a structure of this kind is its very great weight, considering that the cover moves on wheels along a track. On the other hand, even though a great thickness of insulating mass is used, the cover is still heated so much that it tends to warp in the course of time, with the consequence that the masonry develops cracks and the cover loses its tightness. Therefore, repairs and replacement of the cover are necessary from time to time.